Cutter Head

• Dual line cutter head.
  
  Automatic feed spools frequently jam because of overwrapping line. If tapping the spool doesn't restore proper line length, remove the spool and free the line. Prewound spools cost more than bulk line but have fewer problems than spools wound by owners. Manual cutting heads use fixed string lengths--when the line wears short just replace it with new line. With either type, if line breaks at or near the head instead of wearing from the tip, that indicates a problem.
  
  Pressing the machine too quickly into the weeds forces it to cut with the belly of the line rather than the end. A worn cutting head can also develop sharp edges around the line port, shearing it off before its time. Worn-out heads should be replaced.
  
  

Shaft

• If the motor runs properly but nothing happens at the cutter head, the shaft or clutch may be ruined. If it's a clean break, the cutter head will turn freely when spun by hand. If the cutter head is jammed with weeds, the motor will stall--turn the motor off and clear the head. Wrapping the line around solid obstacles may do serious damage to the shaft or clutch. Be careful of wires and don't try to cut stalks or stems beyond the ability of the machine. Cut with the tip of the line and use only as much speed as is necessary for efficient work. Don't run the machine at full throttle constantly.
  
  

Motor

• Most weed trimmers use two-cycle engines running on a mix of gasoline and oil. Poor performance often traces back to the wrong fuel mix. Gas shouldn't be stored over the winter for use the next year, and machines should be run until the tank is empty before storing away for the season.
  
  Start off each season with the right mix and fresh fuel. Check the air filter and either clean or replace it. Clogged air filters cause severe drops in power, hard starting and frequent stalls. Clogged gas filters prevent fuel from reaching the motor, but gas filters seldom cause problems. A common issue is a clogged spark arrester screen at the exhaust port. Designed to catch unburned carbon that may ignite dry grass if expelled, these screens gradually clog and block exhaust fumes, stalling the motor after a brief run. Remove the screen and clean it. Though many people blame spark plugs for any of these issues, the plugs are rarely at fault. Visibly eroded or broken plugs should be replaced. Plugs clogged with oil and carbon should also be replaced, but the real issue is probably elsewhere.
  
  

Operation

• Follow starting procedures exactly. If everything works as it should, machines should start as the manual describes. Yanking the starting cord to the end repeatedly only wears down the cord and shortens its lifespan. Fixing broken cords may require replacement of both cord and return spring. A flooded motor may refuse to start in spite of your best efforts. Open the choke and let the machine sit for half an hour before trying the correct procedure once again.